Patterns of innervation of neurones in the inferior mesenteric ganglion of the cat.

Abstract

SUMMARY1. The patterns of peripheral and central synaptic input to non-spontaneous, irregular discharging and regular discharging neurones in the inferior mesenteric ganglion of the cat were studied in vitro using intracellular recording techniques.2. All three types of neurones in rostral and caudal lobes received central synaptic input primarily from L3 and L4 spinal cord segments. Since irregular discharging neurones received synaptic input from intraganglionic regular discharging neurones, some of the central input to irregular discharging neurones may have been relayed through the regular discharging neurones.3. In the rostral lobes of the ganglion, more than 70 % of the non-spontaneous and irregular discharging neurones tested received peripheral synaptic input from the lumbar colonic, intermesenteric and left and right hypogastric nerves. Most of the regular discharging neurones tested received synaptic input from the intermesenteric and lumbar colonic nerves; none of the regular discharging neurones received synaptic input from the hypogastric nerves. Some of the peripheral synaptic input from the lumbar colonic and intermesenteric nerves to irregular discharging neurones may have been relayed through the regular discharging neurones.4. Axons of non-spontaneous and irregular discharging neurones located in the rostral lobes travelled to the periphery exclusively in the lumbar colonic nerves.5. Antidromic responses were not observed in regular discharging neurones during stimulation of any of the major peripheral nerve trunks. This suggests these neurones were intraganglionic.6. In the caudal lobes, irregular discharging neurones received a similar pattern of peripheral synaptic input as did irregular discharging neurones located in the rostral lobes. The majority of irregular discharging neurones in the caudal lobes projected their axons to the periphery through the lumbar colonic nerves.7. Non-spontaneous neurones in the caudal lobes, in contrast to those located in the rostral lobes, received peripheral synaptic input primarily from the hypogastric

PACAP27 and Other Neuropeptides in the Inferior Mesenteric Ganglionaa

“…Thus, the colon‐IMG reflex functions as a negative feedback control system. A similar peripheral reflex loop between colonic enteric and sympathetic IMG neurons is present in the cat 3‐5 and dog, 6 and there is reason to believe one is present in humans as well. 7‐9 Mechanosensory colonic enteric neurons (colonofugal neurons) project also to sympathetic neurons in the celiac and superior mesenteric ganglia.…”

Characteristics of synaptic input to three classes of sympathetic neurone in the coeliac ganglion of the guinea‐pig.

“…Antidromic responses could be distinguished from ESPs by the time course of the fast-rising electrotonic axon spike observed when the soma was hyperpolarized (Fig. 6Bb, see Jule, Krier & Szurszewski, 1983). Although a proportion of coeliac neurones do not project their axons in the coeliac nerves, and additionally some axons may have been damaged in dissection, antidromic responses in these fine unmyelinated fibres in vitro are often difficult to elicit (see Jule et al 1983), so that the number of failures may be unrealistically high.…”

Electrophysiology of neurones of the inferior mesenteric ganglion of the cat.

“…The regular discharging neurones received synaptic input from all but the hypogastric nerves. A detailed description of the pattern of convergent synaptic input from central and peripheral sources to each of the types of cells in rostral and caudal lobes is described elsewhere (Jule, Krier & Szurszewski, 1983).…”